(a) Field of the Invention
The present invention concerns static induction transistor and integrated circuit device utilizing same, and more particularly it pertains to improved normallyoperated static induction transistor and integrated circuit device utilizing same.
(b) Description of the Prior Art
The static induction transistor proposed by the present inventor may be characterized by its short channel structure and a high resistivity of the channel region. The high resistivity channel region enables one to form a gate-originating depletion region to pinch off the channel region by selecting the value of the gate bias voltage and also the gate-to-gate distance. This gate-to-channel depletion region, when pinching off the channel region, forms a potential barrier for charge carriers travelling between the source and the drain. The short channel structure remarkably reduces the series resistance from the source to the potential barrier, and makes the height of this potential barrier controllable also by the drain voltage, with the assistance of the high resistivity of the channel region. Thus, a static induction transistor realizes unsaturating drain I-V characteristics, as does the vacuum triode tube, in accordance with its operational principle which is to control the potential barrier height by the drain voltage as well as by the gate voltage. Forward biasing of a junction static induction transistor further adds a factor of minority carrier injection from the gate region.
The "pinch-off point" of a static induction transistor has a meaning similar to that of the conventional field effect transistor in the sense that the depletion region traverses the channel region and occupies a total cross section of the channel region at that position, but has a different meaning in the aspect that the pinch-off point in the static induction transistor has a controllable barrier height for those carriers flowing from the source to the drain, whereas the pinch-off point in the conventional field effect transistor has only the extremely narrowed neutral region, but it has no potential barrier. The above difference plus the difference in the magnitude of the series resistance from the source to the pinch-off point serve to produce a remarkable difference in the unsaturating drain I-V characteristics of the static induction transistor and the saturating drain I-V characteristics of the conventional field effect transistor.
A normally-off type static induction transistor is formed by selecting the impurity concentration in the channel region low and the channel width narrow to enable the depletion region due to the gate-to-channel built-in voltage to transverse the channel region and pinch off the current path. Forward bias operation is made possible in such normally-off type static induction transistor, and allows the static induction transistor to advantageously substitute for the bipolar transistor.
An IIL which has been developed as a bipolar logic circuit has the arrangement that the collector electrode of an injector transistor is formed in common with the base electrode of an inverter transistor, and that said inverter transistor is of the upside-down type, and also that the base electrode of this injector transistor is formed in common with the emitter electrode of the inverter transistor. Thus, an IIL has materialized high packing density, high-speed operation and so forth. An IIL type static induction transistor logic circuit which performs a circuit function similar to that of IIL has been proposed and developed also by the present inventor (Electronics Aug. 19, 1976, page 4E), and this circuit exhibits an ability superior to that of the bipolar type IIL. In such known structures, the inverter transistor empolyed has adopted an upside-down type structure, so that these known structures have the drawbacks such that the current injection efficiency and the carrier travelling efficiency from the emitter electrode to the collector electrode or from the source region to the drain region cannot be enhanced substantially. More particularly, in case an upside-down type static induction transistor (SIT) is employed, the drawbacks exist that the transconductance cannot be made large, and that accordingly the operation speed is limited.